This invention relates to parametric test structures for integrated circuits, more particularly, this invention relates to a test structure to measure the progress, completion, and results of through-substrate etching in substrates.
Silicon etching is being aggressively pursued in micro-machining such as with the fabrication of fluid ejection devices such as ink-jet printheads. During the fabrication of such fluid ejection devices, expensive vision tools or high cost operators are used to monitor and measure the parameters of trench etching in silicon or other substrates. Such parameters include trench depth, trench width, and trench length to name a few. Manufacturers have used these visual monitoring techniques even though they are expensive and prone to error especially when manual labor is used. In addition, when these visual monitoring techniques are used in high volume operations, fatigue and other human factor issues such as ergonomics must be factored into the process, thereby increasing costs. Unless an approach is found which reduces the human interaction involved with measuring trench parameters, costs will continue to increase making micro-machining less attractive as a new technology.
A through-substrate etching process is monitored by providing a sacrificial electrode in proximity to a desired etch window on the substrate. An etch process is performed on the substrate. The etch process is monitored by measuring an electrical property of either the substrate or the sacrificial electrode or both.